The present invention relates to a control circuit for regulating current flowing through a load and to a use of such a control circuit More specifically, the present invention relates to a regulator control for a circuit where an AC input is rectified to provide a DC signal which is supplied to a load and wherein a current sensor is coupled by a transformer between the AC input and the rectifier to sense the load current and provide signals to a regulator control. The present invention has particular utility in regulating the cathode current of travelling wave tubes.
German Published Patent Application No. DE-37 41 222 C1, published Dec. 15, 1988, suggests the provision of a current sensor or current converter in a load circuit for "potential free" (e.g., transformer coupled) control of the load current, where the signal to be supplied to a control device was obtained by detecting and rectifying the current with a current sensor.
U. Tietze and Ch. Schenk, in "Halbleiter-Schaltungstechnik" [Semiconductor Circuit Technology], 2nd Edition, 1971, pp. 338 to 340, published by Springer-Verlag discloses the use of a control element in the form of a transistor in a load circuit for regulating the current, where the collector or emitter transistor current is measured with a measuring resistor and the transistor base current is regulated in response to the measured current.
U.S. Pat. No. 4,688,162 Mutch et al. issued Aug. 18th, 1987, discloses a device for regulating the current flowing through a load, where the voltage from an AC source is rectified and thereafter supplied to the load and wherein a current regulator is controlled or regulated dependent on the source and load currents. The AC source current is detected by means of a current detector and is compared with the load current, after having been transformed, and the regulation deviation or difference derived from this comparison is used to control the control element of the current regulator for improving the efficiency of the device. See, in particular the abstract and column 2, line 59 to column 3, line 43, together with FIG. 1.
German Patent No. 31 30 571 C2 of Jul. 21st, 1983, discloses a device in the form of a forward converter for regulating the current flowing through a load R, where a current sensor Dr supplies, free of potential (e.g., transformer coupled), a voltage which is proportional to the load current and which, after having been correspondingly rectified, is used as supply voltage for the control and regulating portion of the forward converter. See, in particular the claim and the drawing figure.
The present invention provides a new and improved form of fast load current regulation wherein the load current is sensed "free of potential," e.g., by use of a transformer.